1. Technical Field
The present invention relates to projection systems and, more particularly, relates to compact projection systems for portable devices.
2. Description of the Related Art
Projectors have been used in rooms to display images for many years. Slide projectors and projection televisions are examples of large-scale projection systems. These projection technologies, however, are unsuitable for compact portable applications.
Miniature optics using a series of lenses and mirrors have been proposed for virtual image viewers on telephones handsets for example, in U.S. Pat. Nos. 6,073,034, 5,867,795 and 5,048,077. These systems provide a personal image viewable by the telephone user through an eye hole or eye piece. These systems can cause user eyestrain over long periods of time. These systems are incapable of presenting large amounts of screen data at once without scrolling an image. These systems are incapable of use by a group of people such as for demonstration purposes at a meeting.
What is needed is a large screen projection system, for use with a portable electronic device, to present to groups of people or allow large amounts of data to be presented without user eyestrain.
A compact real-image projection apparatus is used for a portable device. An optical projector emits light capable of forming an image. A collapsible screen has a collapsed surface area no larger than substantially the surface area of a side of the portable device and an expanded surface area capable of receiving the light emitted from the optical projector. A retractable connecting member is coupled between the screen and the optical projector and has at least a stowed position and an extended position. The extended position is configured to hold the screen and the optical projector relative to one another such that the light emitted from the optical projector forms a real image on the screen. The collapsible screen can be unfolding or rolling, for example. In two alternative embodiments, collapsible screen can be either reflective or transmissive for viewing from either the front or the back of the optical projector. The collapsible screen can have multiple layers with a Fresnel surface and be a gain screen that concentrates reflected or transmitted light in a viewing zone.
The details of the preferred embodiments of the invention may be readily understood from the following detailed description when read in conjunction with the accompanying drawings wherein: